Changes

{{OpenPagesTop}}

{{OpenPagesTop}}

== Introduction ==

== Introduction ==

The three possible areas for aortic stenosis to occur are '''subvalvular or subaortic''' (occurs below the valve), '''valvular or aortic''' (occurs at the valve) and '''supravalvular''' (occurs after the valve).  

The three possible areas for aortic stenosis to occur are '''subvalvular or subaortic''' (occurs below the valve), '''valvular or aortic''' (occurs at the valve) and '''supravalvular''' (occurs after the valve). The most common form is subaortic stenosis (SAS), usually as a consequence of fibrous bands that may be circumferential (severe) or may only affect a small area of the LVOTO. The subvalvular fibrous ring may encompass the anterior mitral valve leaflet, causing it to become immobile.  In subaortic stenosis, the lesions may not be present from birth and may develop or progress as the dog matures; but do not generally progress beyond early adulthood. This is in contrast to valvular aortic stenosis, where the valve may become more stenotic as the dog ages.  

The stenotic area causing the problem is a consequence of fibrous tissue on and around the aortic valve. A narrowing of the aortic outflow tract causes an increase in pressure and this increased pressure leads to ''left ventricular dilation and concentric hypertrophy'' as a means of maintaining sufficient cardiac output. The severity of stenosis determines the extent of hypertrophy. Hypertrophy of the myocardium leads to an increased oxygen demand and decreased diastolic filling and insufficient oxygen to meet the new needs of the hypertrophied left ventricle predisposes the animal to ventricular [[:Category:Arrhythmia|arrhythmias]]. There is also an increased risk of bacterial [[Endocarditis|endocarditis]] in animals affected by this condition.

Aortic stenosis causes an impedence to left ventricular ejection and pressure overload on the left ventricle. The increase in afterload results in a compensatory ''concentric left ventricular hypertrophy'' in attempt to maintain sufficient cardiac output. The severity of stenosis usually determines the extent of hypertrophy. The myocardial hypertrophy results in increased myocardial oxygen demand, beyond the capacity of the coronary capillary vascular bed to supply oxygen. Increased wall stress also compromises coronary perfusion, particularly to the subendocardium. Insufficient oxygen supply to meet the needs of the hypertrophied left ventricle causes myocardial ischaemia and predisposes the animal to ventricular [[:Category:Arrhythmia|arrhythmias]]. There is also an increased risk of bacterial [[Endocarditis|endocarditis]] in animals affected by this condition.

==Signalment==

==Signalment==

This condition is common in dogs, especially the subvalvular lesions. Boxers usually have valvular stenosis. It is rare in cats, but if they are affected, usually they get supravalvular lesions.

Aortic stenosis is one of the three most common congenital cardiac defects in dogs. Predisposed breeds include the Newfoundland, Boxer, German Shepherd, Golden Retriever and Bull Terrier. Boxers usually have valvular stenosis.  

 

Predisposed breeds include the Newfoundland, Boxer, German Shepherd, Golden Retriever and Bull Terrier.  

== Clinical Signs ==

== Clinical Signs ==

As with all heart conditions, weakness, exercise intolerance, syncope, stunting of growth and pallor are all possible clinical signs. However, the disease may be asymptomatic.

Patients may present with exercise intolerance or syncope. However, the disease may be asymptomatic. Lack of clinical signs is not an appropriate reason to delay further investigation of a murmur, as sudden death can be the first indication of aortic stenosis.

== Diagnosis  ==

== Diagnosis  ==

* Left sided, systolic [[Heart Murmurs|murmur]] with point of maximum intensity at the left base with radiation to the right base and thoracic inlet. The murmur grade usually correlates with the severity of the stenosis for fixed obstructions. The disease has a wide spectrum of severity, and low grade murmurs may be difficult to distinguish from physiological murmurs in puppies.

 

Upon physical examination a systolic [[Heart Murmurs|murmur]] will be heard which is '''loudest over aortic valve''' and there may also be '''weak femoral pulses'''.  

 

'''Radiographic''' findings may show '''left ventricular enlargement''' or bulge around the aortic valve, however, radiographs may appear normal due to concentric hypertrophy.

'''Electrocardiography''' (ECG) may show an '''increased R-wave amplitude''' (indicates left ventricular hypertrophy) or '''ventricular arrhythmias''' (only severely affected animals).

* Left ventricular enlargement may be recognised

* Post-stenotic dilatation of the aorta (bulge) on a dorsoventral view

===Electrocardiography (ECG)===

'''Echocardiography''' may show left ventricular concentric hypertrophy, fibrous tissue around aortic valve, dilation of the ascending aorta and dilation of the left atrium.  

* Increased R wave amplitude and prolonged QRS duration (indicates left ventricular hypertrophy)

* Ventricular premature complexes may be present in severe cases, due to myocardial hypoxia and ischaemia.

== Treatment and Control ==

== Management ==

Palliative treatment is usually the treatment of choice. It will attempt to alleviate symptoms without curing disease. Methods include exercise restriction and beta-blockers (prevent/control ventricular arrhythmias).  

The requirement for treatment is dictated by clinical signs and/or disease severity. Palliative treatment is usually the treatment of choice. It will attempt to alleviate symptoms without curing disease. Methods include exercise restriction and beta-blockers for prevention or control of [[:Category:Arrhythmia|arrhythmias]].  

Surgical treatment offers a poor outcome with current methods. One suggested surgery is a balloon valvuloplasty, though it has been performed only with limited efficacy.  

Surgical intervention has been described, but offers no advantage over medical therapy in most cases. Surgery should be considered for dogs with severe stenosis and marked left ventricular hypertrophy. In such cases, surgery should be performed early to minimize ischaemic changes to the myocardium. Surgical options for subaortic stenosis include valve dilation via baloon valvuloplasty or open resection under cardiopulmonary bypass.

== Prognosis  ==

== Prognosis  ==

In mild to moderate cases of the condition&nbsp, there is usually a normal quality of life if there is no progression of the malformation. In severe cases, there is often a poor quality of life. Complications from development of congestive [[Heart Failure|heart failure]] or cardiac arrhythmias can occur, as can sudden death within the first 1-3 years of life.  

The majority of cases are mild, do not require treatment and patients are likely to have a normal lifespan. In severe cases, there is often a poor quality of life. Complications from development of congestive [[Heart Failure|heart failure]] or cardiac [[:Category:Arrhythmia|arrhythmias]] can occur, as can sudden death.  

== References  ==

== References  ==

Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (sixth edition, volume 2), W.B. Saunders Company

 

Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2)W.B. Saunders Company

Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier

Fossum, T. W. et. al. (2013) Small Animal Surgery (fourth edition), Elsevier Mosby

{{review}}

{{review}}